Conventionally, there is known a current detection device which uses a U-shaped magnetic shield in a core-less current detection device from which a magnetic core is excluded. There is a need to make a cross-sectional dimension of the magnetic shield small in order to miniaturize the current detection device. However, a saturated magnetic flux of the magnetic shield is lowered as the cross-sectional dimension of the magnetic shield becomes smaller. The magnetic shield has a magnetism collecting function similarly to the magnetic core. In a case where a hall element detects the magnetic flux, the reduction of the saturated magnetic flux of the magnetic shield results in reduction of a detectable maximum current. Therefore, it is difficult to achieve both the miniaturization of the current detection device and the measurement of a large current in the conventional magnetic shield at the same time. With this regard, there is disclosed a shield structure in JP 2013-195381 A (PTL 1).
In the current detection device of PTL 1, the magnetic shield is configured by a plurality of shield materials. The conductor has a rectangular cross-sectional surface which is short in the vertical direction and long in the horizontal direction. The magnetic shield has two short side walls (side walls) disposed on a side near two short sides of the conductor and one long side wall (bottom wall) disposed on aside near the long side of the conductor. The magnetic shield has a cross section reducing portion such as a gap, a notch, or a through hole in the long side wall, to increase the magnetic flux leaking out to the outside of the magnetic shield and to reduce the magnetic flux passing through the magnetic shield. With the configuration, the measurable maximum current is increased while suppressing the reduction of the saturated magnetic flux of the magnetic shield.